Depression is a mood disorder that affects 17 million Americans each year, and is responsible for 9.7 million doctor visits. It affects sufferers in a variety of ways, resulting in depressed mood, irritability, sleep disorders, feelings of agitation, guilt and worthlessness, loss of energy and initiative, an inability to concentrate and an increased incidence of suicide. There are a number of antidepressant pharmacological agents, and once the proper treatment is determined, their effectiveness is quite high.
Major Depressive Disorder (MDD) is the psychiatric diagnosis most commonly associated with completed suicide. The American Association of Suicidology notes on their website that the lifetime risk of suicide among patients with untreated MDD is nearly 20%. About ⅔ of people who complete suicide are depressed at the time of their deaths. In a study conducted in Finland, of 71 individuals who completed suicide and who had Major Depressive Disorder, only 45% were receiving treatment at the time of death and only a third of these were taking antidepressants.
Evidence suggests that pharmacological treatment of some depressed subjects may increase the risk of suicidal thinking and behavior in adolescents. Development of methods to identify those subjects who are at increased risk of developing adverse events, especially suicide, would provide significant benefit to both patients and clinicians.
Cook et al. demonstrated that pre-frontal electroencephalographic (EEG) cordance, a quantitative EEG (QEEG) parameter, predicts successful response to fluoxetine antidepressant therapy. Greenwald et al. in U.S. patent application Ser. No. 10/337,088 described the use of EEG indices using bispectral features to assess the severity of depression and to predict response to antidepressant pharmacological treatment. It has been reported that side effect burden, characterized as the mean number of side effects per clinical visit, correlated with changes in an EEG index (prefrontal cordance) during the placebo lead-in period in patients receiving antidepressant treatment, but not in a placebo control group.
Others have observed that abnormal electroencephalographic (EEG) activity has been associated with various psychiatric disorders and behaviors, including depression, suicide, and aggression and reported that differences in the intrahemispheric distribution of EEG alpha band power (alpha asymmetry), particularly over posterior regions of the scalp, differed between adolescent female suicide attempters and matched controls. Specifically, the controls exhibited greater EEG alpha band power over right than left hemispheres as compared to suicide attempters. Note that this study was not a prediction of the risk of suicidal behavior, but an observational study of EEG patterns conducted subsequent to suicide attempts. Several researchers have reported that paroxysmal EEG abnormalities increase the risk of suicide in patients.